1. Field of Invention
The present invention relates to a reel on which a fine metal wire is wound. In particular, the present invention relates to a reel for a fine metal wire (hereinafter referred to as just “reel”) designed to wind thereon a fine metal wire, including a wire for a wire saw (hereinafter referred to as “saw wire”) to cut hard material such as artificial crystal, silicon, ceramic, or the like, and a wire for a rubber hose for reinforcement (hereinafter referred to as “hose wire”).
2. Description of the Prior Art
A conventional reel 11 as shown in FIG. 5, has a drum 12, and flanges 13, 13 disposed at the ends of the drum. The drum 12 and the flanges 13 are made of thick steel sheets such as carbon steels for machine structural use (for example, S45C/JIS), or the like. Depending on manufacturing method, some kinds of reels have been known, including an integral reel which is made by cutting out the drum and the flange as one piece, and a welded reel into which three divided parts, namely, the drum and both flanges are welded together.
A fine metal wire to be wound on the above-mentioned reel is, for example, a fine metal wire having a diameter of 0.12 to 0.16 mm or less and serving as a saw wire, or a fine metal wire having a diameter of about 0.20 to 0.80 mm and serving as a hose wire. Also, the fine metal wire, which is to be wound on the described reel, may be, for example, a fine metal wire having a diameter of about 0.15 to 0.40 mm and serving as a wire of a twisting steel cord (namely, a tire cord) for reinforcing rubber products, which contains a steel cord functioning as a metal twisting wire in some cases. In a case where the above-mentioned fine metal wire is wound on the reel under a predetermined tension (for example, a tension of 0.4 kg to 1.5 kg), the winding tension causes a high tightening tension to the drum, thus resulting in applying to the flanges a big force pushing them apart. And this force for pushing apart (hereinafter referred to as “side pressure”) causes the flanges at both ends to be pushed away in a direction that they separate from each other.
As the diameter of the metal wire becomes smaller, or as the winding tension becomes larger, or as the reciprocating number of turns of the wire becomes larger, the side pressure generated becomes larger. For example, in a case where the above-mentioned extra fine metal wire is a saw wire, weight of 40 kg to 60 kg or more is applied to the reel. In this case, the side pressure thereof sometimes reaches several tons or several tens of tons.
To provide sufficient strength and rigidity to withstand such side pressure, the conventional reel 11 utilizes the thick steel sheet having a thickness of about 20 to 50 mm. Accordingly, the conventional reel is so heavy that the operability thereof becomes very poor, and that the reel suffers from the high cost of transportation. Also, the conventional reel suffers from the high cost of materials and treatments.
Additionally, even this mechanically strong reel, since the generated side pressure is excessively large, cannot avoid plastic deformation of the flanges and the drum. After repeated use of several times, or 10 times or more, the deformation of the reel is proceeding, or the reel is broken to become unusable. That is, the conventional reel has a disadvantage that it fails to ensure durability appropriate to the high costs.